Anti-pollution device for a metallurgical vessel

ABSTRACT

A vessel for converting molten ferrous metal to steel is mounted for pivoting about a horizontal axis and has bottom tuyeres which permit blowing of oxygen, other gases and powdered materials upwardly through molten metal inside of the vessel. A smoke hood is engaged with the open mouth of the vessel when it is untilted and is disengaged when the vessel is tilted for discharging or charging it. An enclosure at least partially surrounds the vessel. Devices for producing air curtains are situated adjacent certain openings in the enclosure to prevent influx of air into the enclosure and thereby maintain subatmospheric pressure within it so that smoke is drawn from the enclosure by an exhaust system connected to the hood instead of being released to the atmosphere.

United States Patent 1 Dortenzo 1 Apr. 3, 1973 [54] ANTI-POLLUTIONDEVICE FOR A METALLURGICAL VESSEL [75] Inventor: Alexander T. Dortenzo,Pittsburgh,

[73] Assignee: Pennsylvania Engineering Corporation, Pittsburgh. Pa.

[22] Filed: Oct. 20, 1971 [21] Appl. No.: 190,790

[56] References Cited UNITED STATES PATENTS 8/1957v McFeaters ..266/3512/1961 Bussard et al. ..266/34 V Primary Examiner-Gerald A. DostAttorney-Ralph G. l'lohenfeldt et al.

[57] ABSTRACT A vessel for converting molten ferrous metal to steel ismounted for pivoting about a horizontal axis and has bottom tuyereswhich permit blowing of oxygen, other gases and powdered materialsupwardly through molten metal inside of the vessel. A smoke hood isengaged with the open mouth of the vessel when it is un tilted and isdisengaged when the vessel is tilted for discharging or charging it. Anenclosure at least partially surrounds the vessel. Devices for producingair curtains are situated adjacent certain openings in the enclosure toprevent influx of air into the enclosure and thereby maintainsubatmospheric pressure within it so that smoke is drawn from theenclosure by an exhaust system connected to the hood instead of beingreleased to the atmosphere.

PATENTEDAPRB I975 3,724,827

SHEET 2 OF 2 FIGZ INVENTOR ALEXANDER T. DORTENZO ANTI-POLLUTION DEVICEFOR A METALLURGICAL VESSEL BACKGROUND OF THE INVENTION argon-oxygenconverters and top and bottom-blown basic oxygen converters. Abottom-blown basic oxygen converter is used to illustrate an applicationof the invention. A converter of this type is usually surrounded by anenclosure having a smoke hood near its top connected to an exhaustsystem. When it is desired to tilt the vessel on its horizontal axis fordischarging the molten contents or for introducing scrap and othermaterials through its top mouth, the smoke hood is lifted or otherwiseuncoupled from the vessel and smoke and other gases are able to escapefrom the enclosure and thereby pollute the atmosphere.

When the vessel is uncoupled from its smoke hood, the exhaust systemdraws in atmospheric air through various'openings in the enclosure whichmust necessarily be present for admitting slag ladles, teeming ladlesand the like. There is usually an opening for admitting the spout of ascrap car from which the vessel may be charged with scrap when it istilted toward that opening. The scrap charging operation is usuallyaccompanied by evolution of large quantities of smoke from the vessel.

In top-blown basic oxygen converters, oxygen is introduced into thevessel by means of a lance extending downwardly through the upper end ofthe vessel. In argon-oxygen and bottom-blown converter vessels, theoxygen or other gas is introduced through tuyeres located below thelevel of the molten metal in the vessel. When top-blown basic oxygenconverters are tilted for receiving hot metal and scrap, for example,the oxygen lance is normally turned off. This is also possible inconnection with argon-oxygen converters where the tuyeres are located inthe sides of the vessel so that they would be free of metal when thevessel is tilted. However, in a bottom-blown converter vessel havingtuyeres located in its bottom, gas flow must be maintained at 'all timesto prevent hot metal from flowing into the tuyeres and into the gas feedsystem. The constant flow of gas has a' tendency to force out evengreater quantities of atmosphere polluting gases from the bottom-blownvessel when it is tilted. Increasing the capacity of the exhaust systemto cope with this condition is not only uneconomical but it isimpractical because such exhaust systems usually handle a constantvolume which means that their ability to withdraw gases and smoke isdiminished to the extent that the exhaust system must handle air whichenters the enclosure.

SUMMARY OF THE INVENTION A general object of this invention is toprovide improved pollution control apparatus for steel conversion andother metallurgical vessels.

Another object of this invention is to provide apparatus for inhibitingthe discharge of pollutants from metallurgical vessels when the latterare disengaged from their smoke hoods and are in any of their alternatepositions.

A further object of the invention is to provide apparatus for preventingthe discharge of pollutants from a steel conversion vessel to theatmosphere when the vessel is being charged, teemed, deslagged or itscontents are being sampled, as examples.

Yet another object of the invention is to substantially obviate usingdoors and other closure means to prevent atmospheric air from enteringthe vessel enclosure or the region around it.

These and other objects and advantages of the invention will become moreapparent from a detailed description of a preferred embodiment of theinvention which will be set forth hereinafter in reference to theaccompanying drawings. 7

In general terms, the invention is exemplified by a converter vesselhaving an open upper end, an enclosure substantially surrounding it. Theenclosure has at least one access opening to permit hot metal or scrapto be charged into the vessel and is associated with a system forexhausting the space within the enclosure around the vessel. Atmosphericair is prevented from entering the enclosure and from displacing smokeand gases to the atmosphere by devices which produce air curtains in thevicinity of certain necessary enclosure openings.

- DESCRIPTION OF THE DRAWINGS FIG. 1 is a front elevation view, partlyschematic and partly in section, of a converter vessel associated with apollution control system in accordance with the invention;

FIG. 2 is similar to FIGQl except thatit illustrates tilting theconverter vessel to permit charging it with scrap; and

FIG. 3 is a fragmentary perspective view of a device for creating an aircurtain for the purposes of the inven- DESCRIPTION OF A PREFERREDEMBODIMENT A typical application of the invention is illustrated inFIGS. 1 and 2 in connection with a bottom-blown steel converter vesselwhich is generally designated by the reference numeral 10. Those skilledin the art will appreciate that the invention is applicable to manyother types of metallurgical vessels including top-blown basic oxygenand argon-oxygen systems.

Vessel 10 comprises a metal shell 11 which is lined with refractoryabout its sides 12 and its bottom 13. The top of the vessel has an openmouth 14 as can be seen in the part of the vessel 10 which is brokenaway. The refractory bottom 13 of vessel 10 has several tuyeres 15 whichreceive nozzles such as 16 that extend from a chamber 17. Chamber 17 hasa supply pipe 18 for selectively conveying various gases and powderedmaterials to the chamber and the vessel. These gases and powderedmaterials are forced from the tuyeres through the molten metal withinthe vessel, the top'surface of the metal being indicated by a dashedline marked with the numeral 19. The construction at the bottom of thevessel 10 is only schematized but it will be understood that there maybe one set of centrally located tuyeres 15 for blowing gases, primarilyoxygen, and powdered materials through the melt and there may be anotherset of tuyeres around the periphery through which propane or otherhydrocarbon gas is injected along the interior refractory wall surfacesto prevent their deterioration.

Vessel is supported within a trunnion which has diametrically oppositelyextending trunnion shafts such as 21. The supports in which the trunnionshafts are journaled are omitted as is the drive mechanism for tiltingthe vessel to each of a plurality of positions since the support andtilting mechanism are conventional. It

is sufficient for present purposes to recognize that ves-- sel 10 may becompletely inverted so as to place its mouth 14 at the bottom or it maybe partially tilted to permit charging through mouth 14 with hot metalor scrap or both and it may be tilted to a substantially horizontalposition to permit pouring of molten metal from a suitable spout 22 inthe top side of the vessel. Trunnion shaft 21 is hollow and may beconnected with pipe 18 for conducting gases and powdered materials suchas fluxes and the like to distributor chamber 17. There is usually aswivel joint, not shown, between hollow trunnion shaft 21 forfacilitating connecting a supply pipe, not shown, for gases and powderedmaterials to rotatable trunnion shaft 21.

Vessel 10 is within an enclosure which is generally designated by thenumeral25. The enclosure 25 confines gases evolved from the vessel toits vicinity and acts as ashield for preventing dissemination of slagand molten metal that sometimes sputters from vessels of scrap metal isbeing dumped intothe vessel from a scrap cart 42 from which a spout 43extends into the mouth of vessel 10. Only a fragment of scrap car 42 isshown but those skilled in the art will understand that the cart may runon tracks supported on charging floor 44 and may be adapted forangulation as shown in FIG.

2 so that its contents may be dumped. The scrap han this type when theyare open. The top of enclosure 25 is 1 provided with a sealing annulus26 in which there is an opening 27 surrounded by an angularly downwardlydepending circular flange 28.v Extending through opening 27 are somecomponents of a water cooled smoke hood which is generally designated bythe numeral 30.

All of the structural details of smoke hood 30 are not shown becausehoods of this general type are known in the art. Smoke hood 30 includesa cylindrical water cooled jacket 31 which connects at its lower end toan annular shroud32 the latter of which has a central opening that issubstantially coaxial with the mouth opening 14 of vessel 10.Cylindrical jacket 31 is coupled at its upper end to an exhaust pipe 33which may connect to a stack or to gas cleaning apparatus, neither thestack or the apparatus being shown. In either case, however, a suctionfan or natural draft will normally induce negative or subatmosphericpressure in exhaust pipe 33 and thus effect withdrawal of gases andsmoke from vessel 10 through the hood assembly 30.

Means for lifting hood 30 to disengage it from vessel l0 includes astationary beam or structure 34 on which there are two or more pneumaticcylinders such as 35 and 36. Connecting rods such as 37 are attached at38 to a ring member 39. When a lifting force is exerted on member 39 bycylinders 35 and 36, smoke hood 30 is elevated clear of vessel 10 inwhich case tapered shroud 32 seats in the annulus defined by flange 28as can be seen particularly well in FIG. 2. The seating of shroud 32 inannulus 28 creates a seal which prohibits noxious gases from leaking outof enclosure 25 and atmospheric gases from leaking into it when the hoodis uncoupled or the vessel is tilted.

Enclosure 25 may be provided with one or more openings such as -accessopening 41 for the purpose of introducing various materials such asscrap through the mouth 14 of vessel 10 when it is tilted as appears inFIG. 2. An illustrative case is shown in FIG. 2 where dling device mayactually be a bin or ladle which is handled by an overhead crane insteadof being'a scrap car as shown. Other devices such as additive ladies mayalso be placed in proximity with access opening 41 for introducing theircontents to vessel 10 when the latter is in tilted position.

Enclosure 25 may have other openings too. For instance, there may beopenings such as 46 and 47 to allow positioning a cart 48 in alignmentwith vessel 10. Cart 48 may carry, for instance, a slag pot 49 and ateeming ladle 50. The cart has wheels 51 which run on a track 52 thatextends across the space between openings 46 and 47 within theenclosure.

It is known to those versed in the art that when vessel 10 is tilted forthe introduction of scrap as depicted in FIG. 2, the small negativepressure in exhaust pipe 33 causes an in-rush of air through openingssuch as 46 and 47 in which case the negative pressure within exhaustpipe 33 is usually insufficient to handle both the in-rushing air andthe gases and smoke which evolve from vessel 10 when it is uncoupledfrom hood 30. Since the exhaust system usually handles a constantvolume, some of the smoke gets into enclosure 25 and escapes to theatmosphere through openings such as 41 and around the scrap cart 42 oraround any other device that may be situated in the opening. Some smokemay even exit through lower openings 46 and 47 which account for thefact that prior practice has been to have hinged 'or sliding doorscooperating with openings such as 46 and'47. Doors, of course, must beopened either manually or mechanically at appropriate times and therebyrequire the attention of an operator.

In accordance with the invention, atmospheric air is precluded fromentering enclosure 25 by use of air curtain producing devices such asdevices 55 and 56 which are installed immediately over openings 46 and47 to typify their use. The air curtain device 55, for example, may beabout as long as opening 47. The device is adapted to project a highvelocity sheath or thin stream of air downwardly from it toward thefloor in the direction indicated by the arrows marked 57. As shown inFIG. 3, the typical air curtain device 55 comprises a box in which thereis suitable flow control mechanism, not shown. In the bottom of the boxis a row of holes which are marked 59-and extend longitudinally of thebox. The holes 59 are, of course, on thebottom of box 55 with respect toits orientation in FIG. 1. The sheath of air or air curtain from devices55 and 56 flows at very highvelocity transverse to' the direction inwhich atmospheric air tends to flow through openings 46 and 47. The aircurtain, however, prevents the atmospheric air from penetrating the pathof the high velocity air so Since the air curtains prevent influx oflarge quantities of atmospheric air through major openings such as 46and 47, the negative pressure produced within enclosure 25 when vesselis uncoupled from its exhaust system tends to be maintained. Thisnegative or subatmospheric pressure causes relatively minor quantitiesof atmospheric air to flow into enclosure 25 around the small freespaces which must necessarily be maintained when a scrap cart 42 orother such device is situated in access opening 41. This minor flow ofair does not materially affect the effectiveness of the constant volumeexhaust system in which case the atmospheric air and substantially allof the smoke and noxious gases from the vessel are captured by theexhaust system. Moreover, the in-draft through opening 41 causes smokeand gas from the vessel to be entrained and swept into the exhaustsystem.

Suitable air curtain producing devices are available from variousmanufacturers including, for example, Dynaforce Corporation, Plainview,New York. Generally an air curtain device long enough to span the entirewidth of an enclosure opening will be selected. Wind or atmospheric airflowing at high velocity can be interrupted with the air curtain. Airvelocities on the order of to 35 miles per hour or about 30 feet persecond up to as high as 55 feet per second and even higher can bestopped effectively provided the discharge height of the air curtain isproperly related to the velocity of the air curtain. By way of example,an air curtain velocity of 2,700 feet per minute will effectively stop a20 mile per hour or 30 feet per second wind over a discharge height of20 feet. The same system which has an initial air curtain velocity of6,000 feet per minute will stop a 35 mile per hour wind with a 3,750feet per minute air curtain velocity over a discharge distance of 10feet.

In summary, the foregoing description illustrates how enclosedmetallurgical and other types of vessels which emit smoke, fumes andnoxious gases can be prevented from contaminating the atmosphere withair curtains that assist in maintaining subatmospheric pressure in thevessel enclosure and preclude in-rush of atmospheric air that wouldoverload the exhaust system. Substantially all of the noxious gases andsmoke can now be drawn into the exhaust system and disposed of in a safeand clean manner. The need for providing cumbersome doors and othersealing devices for preventing inflow of air into an enclosure around avessel is obviated and use of auxiliary exhaust systems for augmentingthe main system can also be avoided. Thus,

capital investment in equipment is reduced coextensively with reductionof atmospheric pollutants.

Although the invention has been illustrated and described in respect toone type of converter vessel and associated enclosure, those versed inthe art will appreciate that the new air curtain pollution preventingmeans may be variously used in connection with other metallurgicalvessels. Accordingly, the scope of the invention is to be determinedonly by interpretation of the claims which follow.

I claim:

. l. A system for mitigating atmospheric pollution by a metallurgicalvessel, comprising:

a. enclosure means for a vessel that is adapted for being moved tovarious positions therein, said enclosure means having an access openingand at least another opening,

. exhaust means adapted to develop subatmosphe'ric pressure forwithdrawing gases and smoke from the vessel when the same is coupledwith said exhaust means and for withdrawing the same from v the vesseland said enclosure means when said vessel is uncoupled,

c. air curtain producing means at at least said other opening projectinga high velocity air stream across the opening to limit flow ofatmospheric air into said enclosure through the opening, therebymaintaining subatmospheric pressure in the enclosure so that when saidvessel is uncoupled gases and smoke are inhibited from exiting throughthe access opening.

. The invention set forth in claim 1 including:

. means adapted to retract at least a part of said exhaust means andthereby uncouple the same from said vessel, whereby to provide clearancefor tilting the vessel and presenting an opening thereof in proximitywith said access opening.

. The invention set forth in claim 1 wherein:

. said enclosure means has a plurality of said other openings ofsubstantial size and there is an air curtain producing means at eachsuch opening.

. The invention set forth in claim 2 wherein:

a. said enclosure means has opening through which said exhaust meansextends, and b. said exhaust means has means cooperating with saidlast-named opening to effect a seal when said exhaust means isretracted. 5. A system for mitigating atmospheric pollution from abottom-blown converter vessel, comprising:

a. enclosure means for a converter vessel that is substantiallyvertically oriented when operating normally and thathas a mouth and ismounted for angulating on a horizontal axis for presenting the mouth atvarious positions within the enclosure means, said enclosure meanshaving at least one access opening for introducing materials to thevessel mouth,

. a smoke hood means and an exhaust pipe means connected thereto, saidsmoke hood means being adapted for coupling and uncoupling with respectto said vessel mouth and said exhaust pipe means having subatmosphericpressure developed therein whereby to withdraw gas and smoke pollutantsfrom the vessel and from the enclosure means, and

c. air curtain producing means located in proximity with another openingin said enclosure and adapted to project a high velocity air currentacross the opening to exclude atmospheric air from said enclosure sothat the exhaust means is effective to withdraw air through said accessopening and thereby prevent outflow of pollutants therefrom.

6. Means for preventing air pollution by a metallurgical vessel thatproduces gas and smoke pollutants, comprising:

a. enclosure means substantially enclosing a space occupied by a vessel,said enclosure means having openings,

b. air curtain producing means situated at at least one of said openingsand adapted to project a high velocity air stream substantiallytransversely to the 9. A method for inhibiting flow of pollutants from apath in which atmospheric air tends to flow into metallurgical vessel tothe atmosphere, comprising:

said opening. a. substantially enclosing the vessel in an enclosure, 7.The invention Set forth in Claim 6 wherein! b. extending asubatmospheric pressure producing Said curtain Producing means isSubstantially device to the enclosure for alternately placing thecoex'tenslv? in length i itsfissociated P vessel interior and enclosureinterior in communi- 8'Th emvent1n Set forth m 9 6 wherein: cation withthe device, thereby exhausting pollua. said enclosure means has anaccess opening for tan-ts and charging the vessel, said access openingbeing sized to accommodate a vessel charging means, b. exhaust meansextending into said enclosure and having an inlet adapted to be coupledwith a vessel and to be uncoupled therefrom so as to draw atmosphericair through that part of the access opening which is not occupied by thecharging means. 15

c. concurrently projecting a high velocity curtain of air over asubstantial opening in the enclosure to prevent air at atmosphericpressure from entering the same and from diminishing the subatmosphericpressure produced by the device.

1. A system for mitigating atmospheric pollution by a metallurgicalvessel, comprising: a. enclosure means for a vessel that is adapted forbeing moved to various positions therein, said enclosure means having anaccess opening and at least another opening, b. exhaust means adapted todevelop subatmospheric pressure for withdrawing gases and smoke from thevessel when the same is coupled with said exhaust means and forwithdrawing the same from the vessel and said enclosure means when saidvessel is uncoupled, c. air curtain producing means at at least saidother opening projecting a high velocity air stream across the openingto limit flow of atmospheric air into said enclosure through theopening, thereby maintaining subatmospheric pressure in the enclosure sothat when said vessel is uncoupled gases and smoke are inhibited fromexiting through the access opening.
 2. The invention set forth in claim1 including: a. means adapted to retract at least a part of said exhaustmeans and thereby uncouple the same from said vessel, whereby to provideclearance for tilting the vessel and presenting an opening thereof inproximity with said access opening.
 3. The invention set forth in claim1 wherein: a. said enclosure means has a plurality of said otheropenings of substantial size and there is an air curtain producing meansat each such opening.
 4. The invention set forth in claim 2 wherein: a.said enclosure means has opening through which said exhaust meansextends, and b. said exhaust means has means cooperating with saidlast-named opening to effect a seal when said exhaust means isretracted.
 5. A system for mitigating atmospheric pollution from abottom-blown converter vessel, comprising: a. enclosure means for aconverter vessel that is substantially vertically oriented whenoperating normally and that has a mouth and is mounted for angulating ona horizontal axis for presenting the mouth at various positions withinthe enclosure means, said enclosure means having at least one accessopening for introducing materials to the vessel mouth, b. a smoke hoodmeans and an exhaust pipe means connected thereto, said smoke hood meansbeing adapted for coupling and uncoupling with respect to said vesselmouth and said exhaust pipe means having subatmospheric pressuredeveloped therein whereby to withdraw gas and smoke pollutants from thevessel and from the enclosure means, and c. air curtain producing meanslocated in proximitY with another opening in said enclosure and adaptedto project a high velocity air current across the opening to excludeatmospheric air from said enclosure so that the exhaust means iseffective to withdraw air through said access opening and therebyprevent outflow of pollutants therefrom.
 6. Means for preventing airpollution by a metallurgical vessel that produces gas and smokepollutants, comprising: a. enclosure means substantially enclosing aspace occupied by a vessel, said enclosure means having openings, b. aircurtain producing means situated at at least one of said openings andadapted to project a high velocity air stream substantially transverselyto the path in which atmospheric air tends to flow into said opening. 7.The invention set forth in claim 6 wherein: a. said air curtainproducing means is substantially coextensive in length with itsassociated opening.
 8. The invention set forth in claim 6 wherein: a.said enclosure means has an access opening for charging the vessel, saidaccess opening being sized to accommodate a vessel charging means, b.exhaust means extending into said enclosure and having an inlet adaptedto be coupled with a vessel and to be uncoupled therefrom so as to drawatmospheric air through that part of the access opening which is notoccupied by the charging means.
 9. A method for inhibiting flow ofpollutants from a metallurgical vessel to the atmosphere, comprising: a.substantially enclosing the vessel in an enclosure, b. extending asubatmospheric pressure producing device to the enclosure foralternately placing the vessel interior and enclosure interior incommunication with the device, thereby exhausting pollutants, and c.concurrently projecting a high velocity curtain of air over asubstantial opening in the enclosure to prevent air at atmosphericpressure from entering the same and from diminishing the subatmosphericpressure produced by the device.